I have a basic question or 2, how high is the ranking for you to be a commitment player, and if you are a commitment player does this mean you can't play Challengers, if this is not true how high does the ranking have to be before a player is not allowed to play Challenger's anymore, thanks?

commitment players are the players who were in the top-30 just before the WTF previous year and they are committed for the next civil year (that is the ones who were in the top-30 on the 14th of november 2011 are the commitment players in 2012, the ones who will be in the top-30 next monday will be the committed players for 2013)

Extract of the rulebook about being allowed to play challengers or not :

Quote:

1) Players positioned 1-10 in the South African Airways ATP Rankings (singles)
twenty-one (21) days prior to the first Monday of the ATP Challenger Tour tournament
are prohibited from entering, accepting a wild card and/or competing in a
ATP Challenger Tour tournament. Players who would have been, had they and
all other players entered, a direct acceptance on the original acceptance list for a
Grand Slam are prohibited from entering, accepting a wild card and/or competing
in a ATP Challenger Tour tournament in the first week of the Grand Slam tournament.
2) Players positioned 11-50 in the South African Airways ATP Rankings (singles)
twenty-one (21) days prior to the first Monday of the ATP Challenger Tour tournament
are prohibited from entering but may receive an ATP-approved wild card
in order to compete in the Challenger tournament. The Challenger supervisor
will make wild card determinations consistent with the limitations outlined below.
Players positioned 11-50 are also prohibited from entering, accepting a wild card
or competing in ATP Challenger Tour tournaments that offer less than $50,000 in
on-site prize money.
3) ATP Challenger Tour tournaments scheduled the same week as an ATP World
Tour tournament may offer wild cards to players positioned 11-50 in the South
African Airways ATP Rankings (singles) who have received approval from the
ATP on-site supervisor according to the following breakdown:
$125,000 in prize money up to (2) two wild cards
$100,000 in prize money up to (1) one wild card
$75,000 in prize money up to (1) one wild card
$50,000 in prize money up to (1) one wild card
$35,000 in prize money no wild card
4) ATP Challenger Tour tournaments not scheduled in the same week as ATP World
Tour tournaments, or during the 2nd week of a Grand Slam, ATP World Tour
Masters 1000 Miami and Indian Wells, may offer wild cards to players positioned
11-50 in the South African Airways ATP Rankings (singles) who have received
approval from the ATP on-site supervisor according to the following breakdown:
$125,000 in prize money up to (4) four wild cards
$100,000 in prize money up to (3) three wild cards
$75,000 in prize money up to (2) two wild cards
$50,000 in prize money up to (1) one wild card
$35,000 in prize money no wild card
NOTE: These restrictions apply only to singles draws.
Case: A player ranked between 11-50 asks for a wild card into a
$50,000 ATP Challenger Tour and is denied by the tournament. The
player then signs in for the qualifying. Is he allowed to play qualifying?
Decision: He is allowed to play only if the tournament grants him
a wild card into the qualifying. The WC, however, will not count
against the maximum allowed number of 11-50 players for the
tournament.

I do not believe this is so, because someone I trust in these matters, Yolita, has said what I said in my previous post.

I don't understand what you mean : yes Murray could not have a zeropointer for not respecting his commitment for 4 ATP500 tournaments in the calendar year because he did indeed respect this commitment, but he might have had a zeropointer for not respecting the conditions to withdraw from an ATP500 tournament properly, as Istomin got one. Besides, you can ask Yolita if she trusts me on those matters if you want